In Y3, we will continue our investigation of how aging effects cell activities in regions of the brain which control endocrine functions. The parameters being studied include catecholamine, protein, and RNA synthesis. C57BL/6J male and female mice will be used. The issue of vascular changes during aging in C57BL/6J mice will be studied by histological criteria, by measuring capillary length in the substantia nigra (pars compacta) and by estimating blood volume in various brain regions. BIBLIOGRAPHIC REFERENCES: Finch, C. E. 1975. Neuroendocrinology of aging: a view of an emerging area. Bioscience. 25: 645-650. Finch, C. E. 1976. Neuroendocrine and autonomic aspects of aging. Ch. 10 in Handbook of the Biology of Aging, C. E. Finch and L. Hayflick (ed.). Van Nostrand.